X-ray CT (Computed Tomography) imaging is normally executed in a lying state in which a subject lies on a bed. For this reason, a heat exhaust mechanism provided in the X-ray CT apparatus that executes X-ray CT imaging in the lying state draws, for example, air from the lower portion of the gantry and exhaust the air that has risen inside the gantry from the upper portion of the gantry.
However, when implementing an X-ray CT apparatus (an X-ray CT apparatus also used for standing position imaging) capable of executing imaging in the lying state and recently demanded imaging in standing and sitting states by itself, the direction of the bore of the gantry changes by 90° between the imaging in the lying state and the imaging in the standing and sitting states. For this reason, when the heat exhaust mechanism is provided in the gantry as described above, air is drawn from a side surface and exhausted from a side surface at the time of imaging in the standing or sitting state. That is, the heat exhaust efficiency lowers in the imaging in the standing and sitting states as compared to the imaging in the lying state. In addition, the air is exhausted from the side surface and, for example, a blast of hot air strikes the subject and the operator. This is undesirable from the viewpoint of hygiene. Furthermore, noise generated by air drawing and exhaust is unpleasant for the subject and the operator.